Short-Time Fourier Transform (STFT) in Signal Processing - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the function used for STFT from the scipy library.

Signal Processing

from scipy.signal import [1]

Drag options to blanks, or click blank then click option'

Astft

Bspectrogram

Cifft

Dfft

Attempts:

3 left

💡 Hint

Common Mistakes

Importing 'fft' instead of 'stft'.

Using 'spectrogram' which is related but different.

The stft function from scipy.signal computes the Short-Time Fourier Transform.

2fill in blank

medium

Complete the code to compute the STFT of signal 'x' with a window size of 256 samples.

Signal Processing

f, t, Zxx = stft(x, nperseg=[1])

Drag options to blanks, or click blank then click option'

A256

B512

C128

D1024

Attempts:

3 left

💡 Hint

Common Mistakes

Using too small or too large window size causing poor resolution.

Confusing nperseg with other parameters.

The parameter nperseg sets the window size for STFT. Here, 256 samples is used.

3fill in blank

hard

Fix the error in the code to correctly compute the STFT with a sampling frequency of 1000 Hz.

Signal Processing

f, t, Zxx = stft(x, fs=[1])

Drag options to blanks, or click blank then click option'

A50

B1000

C500

D100

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect sampling frequency causing wrong frequency axis.

Confusing fs with window size.

The fs parameter specifies the sampling frequency. Here, it should be 1000 Hz.

4fill in blank

hard

Fill both blanks to compute the STFT with a Hann window and 50% overlap.

Signal Processing

f, t, Zxx = stft(x, window=[1], noverlap=[2])

Drag options to blanks, or click blank then click option'

A'hann'

B128

C256

D'hamming'

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'hamming' instead of 'hann' window.

Setting overlap equal to window size or zero.

The Hann window is specified by 'hann'. For 50% overlap with window size 256, noverlap is 128.

5fill in blank

hard

Fill all three blanks to create a dictionary with frequencies as keys (rounded) and maximum magnitude of STFT for each frequency.

Signal Processing

max_magnitude = [1]([2][i].round().astype(int): abs(Zxx[i]).max() for i, [3] in enumerate(f))

Drag options to blanks, or click blank then click option'

Adict

Bf

Cfreq

Dlist

Attempts:

3 left

💡 Hint

Common Mistakes

Using list instead of dict.

Using wrong variable names causing errors.

The code creates a dictionary (dict) mapping rounded frequencies (f) to max magnitude. The loop variable for frequency is freq.